Calbuco seen from north with Lago Llanquihue in foreground, October 1996
volcano number: 1508-02= (according to Volcanoes of the World, 1994 edition)
summit elevation: 2003 m
location: 41.326°S, 72.614°W
North flank of Calbuco
(Full picture JPEG: 45K) View of Calbuco volcano from the north, showing strongly dissected older edifice to the right and active part of the volcano on the left. The historically active crater lies in the smooth, snow-covered area to the left. One of the 1961 lava flows (with distinct levees) extends down from the central part of the volcano, where the younger part of the edifice abuts against the older part. Photo by Werner Keller, January 1991.
Although less frequently active than Villarrica and Llaima to the north, Calbuco is one of Chile's most notable volcanoes, due to the violence of its eruptions and to the formation of large lahars during its eruptions. Based on the fact that Calbuco erupts once about every 30 years, and on a recent increase of its fumarolic activity, the volcano might be expected to be the most likely candidate for Chile's next large eruption.
Calbuco has grown during at least two stages, of which an older, strongly dissected edifice in the W part of the volcano and a younger one containing the active crater give testimony. The summit area is occupied by a plateau-like feature about 1.5 km in diameter with the active crater in its NE part. This plateau is covered with thick snow and glacial ice all year round, thus the main hazard from the volcano in the case of renewed activity is from snowmelt with the resulting formation of lahars and meltwater floods. All historical eruptions have produced lahars, causing damage in this area which, until the time of the most recent eruption, in 1961, has been little inhabited.
Eruptions from Calbuco are both explosive and effusive, and both types of activity are very likely to produce lahars during future eruptions. Another hazard is that from airborne tephra that may reach great distances from the volcano in the case of strong explosive activity (like in 1893) and may threaten aircraft flying near the volcano.
Calbuco seen from Puerto Montt, 1996
(Full picture JPEG: 45K) Calbuco seen from Puerto Montt, situated about 25 km SSW of the volcano. Old part of the volcano with highest summit lies to the left, with the historically active part to the right of it. The active crater lies behind the smooth, ice-covered, dome-shaped feature. Photo taken by Werner Keller in January 1996.
The record of Calbuco eruptions is very short, starting only in the late 19th century. A 1837-38 eruption listed in older compilations has recently been re-attributed to Osorno.
The first historically documented eruption began on 7 January 1893 and lasted until mid-January 1894. The initial phase of this eruption was violently explosive and led to the generation of destructive lahars. During the later stages of the activity, the volcano may have extruded lava although this is not certain.
Minor eruptions occurred in 1895, 1906, on 22 April 1907, in March 1909, and in 1911-1912; none of these events produced lava flows or lahars.
A significant eruption occurred again in April 1917 when a lava dome began to fill the crater left by the 1893-94 eruption, and overflowing lava melted part of the summit icecap. Resulting lahars caused damage along the main rivers draining the volcano.
1929 eruption of Calbuco
(Full picture JPEG:100K) Calbuco in eruption, 6 January 1929. Photo by Karl. Scanned from original print provided by Werner Keller. This photo was also published on the front page of Volcano Letter No. 284 (5 June 1930).
Another major eruption occurred in January 1929. The exact dates of the beginning and end of this event are not known, but the photo above was taken on 6 January, reportedly on the day "after a large explosive eruption". Eyewitness accounts speak of "total darkness" in the area of Lago Todos los Santos whose W shore lies about 25 km from the volcano's summit. The activity lasted only four days and produced lava flows, glowing avalanches, and the resulting lahars caused devastation in valleys around the volcano. Evidence for glowing avalanches was found by Stone (1935) who reports that "brush and small trees (...) were slightly charred, killed, and partly buried by some furious wind or blast of ash that swept with devastating effect down the [Rio Blanco] valley" and "some cattle were killed [in the same area], seemingly burned to death by hot ash".
Ash emission from two vents, 1961
(Full picture JPEG: 83K) Aerial view of Calbuco from SW, showing Somma-like rim of older edifice with highest summit in the foreground and the active crater in eruption. Two boccas are emitting dark ash plumes, the near one being the more active. Date of photograph is unknown but apparently shows late stage of eruption when effusve activity had ended and the eruption became more explosive. Lago Todos los Santos is in the right background. Scanned from original photo provided by Werner Keller.
The most recent eruption from Calbuco occurred in February-March 1961. Minor explosive activity began in late January but more significant activity started on 1 February with the extrusion of a new lava dome that broke through the glacier filling the summit crater. Immediately after the onset of the activity, a lahar rushed down the flanks of the volcano and reached the shore of Lake Llanquihue, about 10 km N of the summit. Later, two thick and broad tongues of lava began to extend from the dome over the NE and SE crater rims and down the flanks of the volcano. With time, the activity became more and more explosive, culminating in a large explosion on 10 March (see photo below). This event produced a tephra column that rose about 15 km above the summit and dropped meter-sized blocks at 0.5 km distance from the crater. Minor activity continued for about one week; since then (that is, since more than 35 years) Calbuco has been quiet, with the exception of a weak explosive eruption in 1972.
Explosive eruption of Calbuco, 10 March 1961
(Full picture JPEG: 59K) Previously unpublished photo of the explosion of Calbuco on 10 March 1961. An eruption column is rising about 15 km above the summit and mushrooming at its top. Scannned from original provided by Werner Keller.
Stronger than usual fumarolic activity from the summit crater began to be noted by nearby residents in May 1995, and on 12 August 1996, a large steam plume was observed above the summit (report by H. Moreno R. on Volcano Listserver). An overflight by Christian Brellenthin (a resident of the area) on 12 October 1996 revealed an ice-free crater (probably formed in 1961) about 50-100 m in diameter showing very weak fumarolic activity (information supplied by Werner Keller).
Casertano L (1962) La actividad volcanica en Chile durante 1961. Boletín de la Universidad de Chile, No. 30 (June 1962): 40-45.
López-Escobar L, Parada M, Moreno H, Frey FA & Hickey-Vargas RL (1992) A contribution to the petrogenesis of Osorno and Calbuco volcanoes, Southern Andes (41°00'-41°30'S): comparative study. Revistia Geológica de Chile vol. 19: 211-226.
Stone JB (1930) Two active volcanoes of Chile. The Volcano Letter No. 284 (5 June 1930). All issues of the Volcano Letter were re-printed in 1987 by the Smithsonian Institution.
Stone JB (1935) The volcanoes of Southern Chile. Zeitschrift für Vulkanologie vol. 16: 81-97.